1. Field of the Invention
The present invention relates to an automobile interior headliner member which is a headliner material of an automobile and an automobile interior headliner molding or forming member to be used for the molding or forming of the headliner member and also to a laminate to be molded or formed to conform to a flat or curved shape.
2. Description of the Related Art
As a base material conventionally employed for an interior headliner material of an automobile, known are that obtained by adding specific thermosetting fibers to split natural fibers or synthetic fibers to form a predetermined fiber mixture and then applying a uniform pressure to the mixture to impart it with a curved face; that obtained by sandwiching a paper corrugated sheet between hot presses, thereby forming it to have a curved face; that obtained by kneading talc or glass fibers in a polypropylene sheet; and a plastic sheet member obtained by adhering a styrene film to an expanded polystyrene, sheet.
The molding or forming members obtained from such combinations involve a problem in molding or forming efficiency or cost, or molded or formed products of them have both merits and demerits in heat resistance, moisture resistance and size stability of the product. Particularly, those obtained by kneading glass fibers in a polypropylene sheet are excellent in the post-molding or -forming properties such as heat resistance, moisture resistance and size stability, but a marked improvement in the working environment in their production step is required or their disposal method is limited, for example, they must be reclaimed even if incinerated after use owing, to the glass fibers mixed therein.
Injection molded products obtained by mixing an inorganic material such as mica or talc in a polypropylene resin in order to improve their rigidity and heat resistance are well known as industrial materials used for automobiles or light electric appliances Injection molded products are however not preferred for their heaviness. A technique of combining an extruded plastic sheet and expanded. polypropylene is known as that for imparting an interior headliner molding or forming member with the advantage of mica and at the same time, for decreasing its weight. When the mica-containing layer is a single layer, however, the rigidity is not improved sufficiently. In addition, a propylene-mica kneaded resin is accompanied with the problem in an extrusion film-forming property, more specifically, the property to form a wide sheet as thin as 300 xcexcm or less, which is the target thickness of the present inventor.
As described above, a molding or forming material which uses, for weight reduction, expanded polypropylene as a base and a mica-containing polypropylene sheet in combination is recognized to have improved rigidity and heat resistance, but it is also necessary to further improve the size stability and decrease sagging at high temperatures to satisfy the demand for an improvement in the size accuracy of an interior headliner material.
Accordingly, an object of the present invention is to provide a complex material having a new constitution obtained by kneading a polypropylene resin and mica, molding or forming kneaded mass into a thin sheet, and then stacking the thin sheet over an expanded polypropylene sheet; and moreover to provide an automobile interior headliner molding or forming member which is improved in the film-forming property of the resin into the mica-containing polypropylene sheet even if the sheet is wide and thin, has high rigidity, is good in working properties upon attachment, has excellent formability upon pressing, is equipped with post-molding or-forming properties such as heat resistance, moisture resistance and size stability, and permits a weight reduction.
With a view to overcoming the above-described problems, the below-described aspects are embraced in the present invention.
In a first aspect of the present invention, there is thus provided an automobile interior headliner molding or forming member (a member used for molding or forming an automobile interior headliner member) comprising a three-layer complex plastic sheet material having formed of an expanded polypropylene sheet and mica-containing polypropylene sheets stacked on both sides thereof, wherein the three-layer complex plastic sheet material is obtained by kneading mica having a particle size of 10 to 100 xcexcm and a polypropylene resin having a melt flow rate (in accordance with Method B of JIS-K-7210) of 3 to 40 g/10 min as measured at a testing temperature of 230 xc2x0 C. under a test load of 21.18 N, forming the resulting mica-containing resin having a mica content of 15 to 40 wt. % into a mica-containing polypropylene sheet having a thickness of 100 to 300 xcexcm and then stacking the mica-containing polypropylene sheet over each of the both sides of the expanded polypropylene sheet having an expansion ratio of 5 to 50 times and a thickness of 2 to 6 mm.
The present invention has thus actualized an automobile interior headliner molding or forming member which is light in weight and excellent in rigidity by employing a three-layer complex plastic sheet material comprising an expanded polypropylene sheet and a mica-containing polypropylene sheet stacked over both sides thereof.
As the expanded polypropylene sheet to be used in the present invention, an atmospherically expanded and crosslinked polypropylene sheet is suited.
In a second aspect of the present invention, there is also provided an automobile interior headliner molding or forming member according to the first aspect of the present invention, wherein on the surface of the mica-containing polypropylene sheet constituting the surface side of the three-layer complex plastic sheet material, that is, the indoor side of the automobile headliner, a reinforcing portion has been partially formed using the mica-containing polypropylene sheet.
In a third aspect of the present invention, there is also provided an automobile interior headliner molding or forming member according to the second aspect of the present invention, wherein the reinforcing portion has been formed by partially adhering, to the surface of the mica-containing, polypropylene sheet (indoor side of the automobile headliner material) constituting the three-layer complex plastic sheet material, another mica-containing polypropylene sheet similar in material quality to said mica-containing polypropylene sheet.
In this third aspect of the invention; the another mica-containing polypropylene sheet partially adhered to the surface side (indoor side) preferably has the same material quality with that of the mica-containing polypropylene sheet which constitutes the surface side of the three-layer complex plastic sheet material, but these polypropylene sheets may be a little different in material quality within an extent of the first aspect of the present invention.
In this third aspect of the present invention, in the stage prior to press forming, the another mica-containing polypropylene sheet to be partially adhered to the surface side (indoor side) may only temporarily be adhered to the surface-side-constituting mica-containing polypropylene sheet of the three-layer complex plastic sheet material. This portion is molten and then adhered by heat when the automobile interior headliner member is formed by press forming under heat.
In this third aspect of the present invention, the mica-containing polypropylene sheet on the surface side (indoor side of the automobile headliner material) becomes partially thick, which however does not cause any problem in appearance because the step difference at the boundary between thin and thick portions disappears by press forming into the automobile interior headliner member under heat.
In a fourth aspect of the present invention, there is also provided an automobile interior headliner molding or forming member according to the second aspect of the present invention, wherein upon extruding the mica-containing polypropylene sheet constituting the surface side of the three-layer complex plastic sheet material, that is, the indoor side of the automobile headliner material, and then stacking the extruded sheet on the expanded polypropylene sheet, said reinforcing portion has been formed thick on the surface side of the mica-containing polypropylene sheet by changing the lip clearance of the discharge portion of the extruder in order to thicken a site which requires sufficient strength, thereby increasing the strength threat.
Also in this fourth aspect of the present invention, the mica-containing polypropylene sheet on the surface side (indoor side of the automobile headliner member) becomes partially thick, but it does not cause any problem in appearance because a change in the lip clearance can be carried out smoothly and the step difference at the boundary between the thick and thin portions can be eliminated by heating and pressurization upon press forming of an automobile interior headliner member.
In a fifth aspect of the present invention, there is also provided an automobile interior headliner molding or forming member according to any one of the second to fourth aspects of the present invention, wherein the reinforcing portion of the mica-containing polypropylene sheet constituting the surface side of the three-layer complex plastic sheet material, that is, the indoor side of the automobile headliner, is disposed along the outer edge (meaning a region having a predetermined width a long the outer edge) and/or along the central portion (meaning a region having a predetermined width along the center) of the complex material.
In this invention, it is possible to thicken either one of the slender central region along the extruding direction of the resin of the three-layer complex plastic sheet material or slender regions on the both sides along the extruding direction of the resin. Or, both may be thickened. Alternatively, a slender central region along a direction vertical to the extruding direction of the resin or slender regions on both sides along a direction vertical to the extruding direction of the resin may be thickened. Or, both may be thickened.
In a sixth aspect of the present invention, there is also provided an automobile interior headliner molding or forming member according to any one of the first to fifth aspects of the present invention, wherein a back treating material has been adhered to the back side of the complex plastic sheet material having a three-layer structure. The term xe2x80x9cback treating materialxe2x80x9d as used herein means a material to be adhered for preventing frictional noises caused by oscillation during automobile traveling.
In a seventh aspect of the present invention, there is also provided an automobile interior headliner member obtained by molding or forming an automobile interior headliner molding or forming member according to any one of the first to six aspects of the invention, wherein the mica-containing polypropylene sheet constituting the back side (a side opposite to the indoor side of the automobile headliner) of the three-layer complex plastic sheet material partially has a ruggedness and the mica-containing polypropylene sheet (the indoor side of the automobile headliner) has a substantially flat surface without ruggedness.
In an eighth aspect of the present invention, there is also provided an automobile interior headliner member formed using an automobile interior headliner molding or forming member according to anyone of the first to the sixth aspects of the present invention, which has further a layer of a resin laminate paper outside the mica-containing polypropylene sheet constituting the back side of the three-layer complex plastic sheet material.
The above-described layer of a resin laminate paper may be disposed by directly adhering it to the backside of the three-layer complex plastic sheet material or by forming another layer such as a layer of a back treating material on the back side of the three-layer complex plastic sheet material and then adhering outside thereof the resin laminate paper.
In a ninth aspect of the present invention, there is also provided an automobile interior headliner molding, or forming member according to any one of the first to sixth aspects of the present invention, which has a maximum flexural load at break of 9.8 to 49.0 N as measured at a bending test by applying, at a rate of 50 mm/min, a load to a test piece of 50 mmxc3x97150 mm at the center of 100 mm span length supported freely at both ends until the member is broken.
The maximum flexural load of 9.8 to 49.0 N is a value which an automobile interior headliner member is essentially required to have. This value can also be applied to an automobile interior headliner molding or forming member when it is not subjected to special processing for imparting it with strength upon molding or forming of an automobile interior headliner molding or forming member prior to molding or forming into a headliner member.
In a tenth aspect of the present invention, there is also provided an automobile interior headliner member according to the seventh or eighth aspect of the present invention, wherein the maximum flexural load at break is 9.8 to 49.0N as measured at a bending test by applying, at a rate of 50 mm/min, a load to a test piece of 50 mmxc3x97150 mm at the center of 100 mm span length supported freely at both ends until the member is broken.